In the bread-making process it is known to add bread-improving and/or dough-improving additives to the bread dough, the action of which, inter alia, results in improved texture, volume, flavour and freshness of the bread as well as improved machinability of the dough.
In recent years a number of enzymes have been used as dough and/or bread improving agents, in particular, enzymes which act on components present in large amounts in the dough. Examples of such enzymes are found within the groups of amylases, proteases, glucose oxidases and (hemi)cellulases, including pentosanases.
EP 321 811 and EP 338 452 disclose the use, in baking, of glucose oxidase in combination with other enzymes (sulfhydryl oxidase, hemicellulase, cellulase). Glucose oxidase catalyzes the oxidation of .beta.-D-glucose to produce D-glucono-1,5-lactone and hydrogen peroxide.
Pyranose oxidases are enzymes which catalyse the oxidation of several monosaccharides at position C2 with the concomitant release of hydrogen peroxide. Glucose, in its pyranose form, tends to be the preferred substrate. However, a number of other substrates, e.g., furanoses such as xylose, can also be oxidised by the enzyme. The reaction product of glucose oxidation is 2-keto-glucose, and of xylose oxidation, 2-keto-xylose. The pyranose oxidase is distinct from glucose oxidase (E.C.1.1.34) which catalyses the oxidation of glucose at position C1 with the concomitant formation of gluconic acid.
Pyranose oxidases are of widespread occurrence, but in particular, in Basidiomycete fungi. Pyranose oxidases have been characterised or isolated, e.g., from the following sources: Peniophora gigantea (Huwig et al., 1994, Journal of Biotechnology 32, 309-315; Huwig et el., 1992, Med. Fac. Landbouww, Univ. Gent, 57/4a, 1749-1753; Danneel et al., 1993, Eur. J. Biochem. 214, 795-802), genera belonging to the Aphyllophorales (Volc et al., 198S, Folia Microbiol. 30, 141-147), Phanerochaete chrysosporium (Volc et al., 1991, Arch. Mirobiol. 156, 297-301, Volc and Eriksson, 1988, Methods Enzymol 161B, 316-322), Polyporus pinsitus (Ruelius et al., 1968, Biochim. Biophys. Acta, 167, 493-500) and Bierkandera adusta and Phebiopsis gigantea (Huwig et al., 1992, op. cit.)
The use, in baking, of a pyranose oxidase has never been suggested before.
It is the object of the present invention to improve the properties of dough and/or baked products by the use of a pyranose oxidase enzyme.